Method for the preparation of perfluoroethers

ABSTRACT

A method for synthesizing perfluoropolyethers by effecting addition reactions under low temperature photolysis between perfluoroolefins, perfluorodialkyl peroxides and fluoroxyperfluoroalkanes resulting in the synthesis of new compounds.

STATEMENT OF GOVERNMENT INTEREST

The invention described herein may be manufactured and used by or forthe Government for governmental purposes without the payment of anyroyalty thereon.

BACKGROUND OF THE INVENTION

This invention relates to novel perfluoroether-forming reactions and tothe products produced thereby. In a more particular aspect, thisinvention concerns itself with new additional reactions of fluoroxygroups to unsaturated perfluorocarbon bonds which are induced throughphotolysis. The resultant products find utility for applications in avariety of instruments and devices in the electrical-electronicair-space, chemical and communication industries. For example, theproducts of this invention can be used as a heat or pressure transfermedium, an inertia-compensating medium or a dielectric coolant.

The increased interest and use of fluorocompounds for industrialapplications has provided an impetus for a continuing research effort inan attempt to develop newer and even more useful products. For example,it is known that addition of fluoroxy groups to perfluoroaromaticcompounds results in the synthesis of interesting perfluoroethers. Thisis exemplified by the addition reaction of trifluoromethyl hypofluoriteto hexafluorobenzene at 40° C for one hour to form bis(trifluoromethyl)peroxide as the main by-product and a mixture of 1,4-monofluoroxy anddifluoroxy adducts.

In continuing the above research, it was unexpectedly found that noveland even more interesting perfluoroethers could be synthesized byutilizing photolysis as a reaction parameter. The photolytic reactionstook place at low temperature resulting in the discovery of novelchemical routes for the synthesis of new perfluoroethers. To be morespecific, photolysis created a reaction condition that permitted theaddition of perfluorodialkyl peroxide and fluoroxyperfluoroalkanes toperfluoroolefins and perfluoroaromatics. The resultant products findutility as fluids for a variety of instruments and devices and as liquidscavengers for neutral and ionic compounds, particles or pollutants.

SUMMARY OF THE INVENTION

The present invention concerns itself with addition reactions betweenfluoroxy groups and perfluoroaromatic which result in the formation ofnovel perfluoroethers. The synthesis of these novel perfluoroesthers isachieved by effecting a reaction under photolysis at low temperature.The reactions involve perfluorodialkyl peroxides,fluoroxyperfluoroalkanes and perfluoroolefins.

Accordingly, the primary object of the invention is to provide newchemical routes for the synthesis of perfluoroethers.

Another object of this invention is to provide novel perfluoroethercompounds that find utility instrumentation fluids because of theirchemical and thermal stability and resistance to the degradative effectsencountered in chemical, high temperature and radiation environments.

The above and still further objects and advantages of this inventionwill become more readily apparent upon consideration of the followingdetailed description of its preferred embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with this invention, it has been found that theabove-described objects can be accomplished by effecting photolyticaddition reactions between equimolar amounts of certain fluoroxycompounds and perfluoroaromatic compounds.

The novel reactions of this invention evolved from a continuing researcheffort into developing new perfluoroether-forming processes. Duringprevious investigations it was reported that the addition reaction of afluoroxyperfluoroalkane, such as trifluoromethyl hypofluorite tohexafluorobenzene at 40° C for one hour formed bis(trifluoromethyl)peroxide as the main by-product and a mixture of 1,4- 1,2 monofluoroxyadducts. However, in accordance with the teachings of this invention,the same reaction was repeated but under photolysis at the lowtemperature of -60° C for 1 hr followed by -20° C for 1 hr. Gaschromatograph separation of the reaction products revealed the presenceof five fractions, which exhibit identical parent mass m/s value of1254, but with different mass cracking patterns. The fraction with thelongest retention time was a minor isomer and a dimer of (CF₃ O)₃ C₁₂F₁₂. The elemental analysis by mass spectroscopic molecular weight (CEC21-110-B) of (CF₃ O)₃ C₁₂ F₁₂ : Found, 626,9525. Calculated for C₁₅ F₂₁O.sub. 3, 628,9512.

As a result, additional efforts were made to effect a photolyticreaction between fluoroxyalkanes and perfluoroolefins. The success ofthis effort is shown in the following equations (1) and (2) wheretrifluoromethyl hypofluorite is reacted with perfluorocyclohexene inequimolar amounts to produce quantitative yields ofperfluoromethoxycyclohexane; and perfluoro-t-butyl hypofluorite isreacted with perfluorocyclopentene in equimolar amounts to produceperfluoro-t-butoxycyclopentane.

A. Photolysis of fluoroxyperfluoroalkanes and perfluorocycloolefins##STR1##

Equation (3) above represents a reaction similar to that demonstrated byequation 2 with the exception that perfluorocyclopentene was replaced byperfluorocyclohexene with all other reaction conditions being equal.

Further research into attempts at effecting a photolytic reactionbetween perfluorodialkyl peroxides and perfluorocycloolefins resulted inthe synthesis of two new vicinal perfluorodi-t-butoxy-cycloalkanes.These two new compounds, vicinal perfluorodi-t-butoxycyclopentane andvicinal perfluorodi-t-butoxycyclohexane are shown as the products ofequations (4) and (5) in which bis(perfluoro-t-butyl) peroxide isreacted with perfluorocyclopentene and perfluorocyclohexene in equimolaramounts under a quartz 200-watt mercury arc at -20° C for one hour.However, in order to synthesize two other novel perfluoroethers asdemonstrated in equations (6) and (7) a 2500 watt source is required.The main products are 2,2'-perfluorodimethoxy-dicyclopentyl and2,2'-perfluorodimethoxydicyclohexyl which result from reactingbis(trifluoromethyl) peroxide with perfluorocyclopentane andperfluorocyclohexene.

B. Photolysis of perfluorodialkyl peroxides and perfluorocycloolefins.##STR2##

From a consideration of the foregoing, it can be seen that the presentinvention provides new chemical routes that comprise a simple andefficient means for preparing novel perfluoroether compounds. Thesecompounds find wide utility in the electronic and chemical industries asfluids for instruments and devices. Their chemical and thermalstability, as well as their resistance to chemicals, thermal andradiation hazards make them especially amenable for use in modern dayhigh speed and high altitude aircraft.

While the invention has been described with particularity in referenceto specific embodiments thereof, it is to be understood that thedisclosure of the present invention is for the purpose of illustrationonly, and is not intended to limit the invention, the scope of which isdefined by the appended claims.

What is claimed is:
 1. A method for preparing perfluoropolymers whichcomprises the steps of (A) forming a reaction mixture of (1) aperfluoroalkyl dioxide and (2) a perfluorocycloolefin; (B) subjectingsaid mixture to photolysis for a period of time and at a temperaturesufficient to effect a reaction therebetween; and (c) separating theresultant reaction products.
 2. A method in accordance with claim 1wherein said perfluoroalkyl peroxide is bis(perfluoro-t-butyl) peroxideand said perfluorocycloolefin is selected from the group consisting ofperfluorocyclopentene and perfluorocyclohexene.
 3. A method inaccordance with claim 2 wherein said photolysis is induced by a 200-wattquartz mercury light source for a period of about one hour at atemperature of about -20° C.
 4. A method in accordance with claim 1wherein said perfluoroalkyl peroxide is bis(trifluoromethyl) peroxideand said perfluorocycloolefin is selected from the group consisting ofperfluorocyclopentene and perfluorocyclohexene.
 5. A method inaccordance with claim 4 wherein said photolypsis is induced by a2500-watt quartz mercury light source for a period of about three hoursat a temperature of about -20° C.
 6. A method for preparingperfluoroethers which comprises the steps of (A) forming a reactionmixture of (1) a fluoroxyperfluoroalkane and (2) a perfluorocycloolefin;(B) subjecting said reaction mixture to photolysis for a period of timeand at a temperature sufficient to effect a reaction therebetween; and(C) separating the resultant reaction products.
 7. A method inaccordance with claim 6 wherein (A) said fluoroxy-perfluoroalkane isselected from the group consisting of trifluoromethyl hypofluorite andperfuoro-t-butylhypofluorite and (B) said perfluorocycloolefin isselected from the group consisting of perfluorocyclopentene andperfluorocyclohexene.
 8. A method in accordance with claim 7 whereinsaid photolysis is induced by 2500-watt quartz mercury light source fora period of about three hours at a temperature of about -20° C.